1. Field of the Invention
The present invention relates to the field of electrical machines. It relates to a high-voltage insulated stator winding having at least one stator winding bar for an electrical machine, which stator winding bar is surrounded by winding insulation which comprises a plurality of insulating layers arranged one above the other, in which case each insulating layer is composed of an insulating material arranged on a base, in particular in the form of Mica paper.
Such a stator winding, in which a fabric or a non-woven is used as the base for the Mica paper, is generally known from the prior art.
2. Discussion of Background
In high-voltage generators, as are used for generating electricity, or high-voltage motors, the stator winding is normally composed of winding bars which are inserted into corresponding slots in the laminated stator core, and are fixed there. For insulation from the laminated stator core, the stator winding is surrounded by winding insulation which is resistant to high voltage, and a number of layers of which are wound as a strip around the winding bars and are subsequently impregnated with (solvent-free) impregnation resin. The insulating winding strip is essentially composed of Mica paper, which, for mechanical reasons, is applied to a base and is connected to this base. A fabric or non-woven composed of insulating material (glass or plastic fibers) is normally used as the base material. In this case, the base also provides the intermediate spaces which are required for the subsequent impregnation.
Increasingly stringent requirements for the withstand voltage of any given material for the winding insulation are leading to an increase in the thickness of the insulation and in the number of wound layers. However, as the thickness increases, the heat transfer between the winding and the laminated stator core deteriorates at the same time, and this is leading to problems in the dissipation of heat losses. Furthermore, for any given stator geometry, the winding must be designed with a smaller conductor cross section, thus resulting in a reduction in the power generated.